NEW YORK — Yankees fans have historically been obsessed with the Red Sox and for good reason – this is a gripping blood feud that that’s lasted for almost a century. But the ticket buyers in the Bronx got a wake-up call during this week’s showdown with the Indians, starting when Corey Kluber out-pitched Luis Severino Monday night, followed by Wednesday's doubleheader sweep. The message couldn’t have been clearer.

For all the mental energy devoted to the Red Sox, it’s the Indians who pose the biggest threat to American League opponents. And yes, that means the Astros, who were crowned in early summer as the AL team most likely to end up in the World Series against the Dodgers. But thanks to their pitching, the Indians have been the better club since Aug. 1 and show no signs of regression.

That’s specifically bad news for the Yankees, who saw their best pitcher, Severino, get out-pitched by Kluber on Monday and never recovered while getting swept. The same goes for the Red Sox, whose own Terminator, Chris Sale, has given up 13 runs in his last eight innings against Cleveland.

There are plenty of reasons why the Indians are on a roll, picking up where they left off from last year. But outsiders focus on two key assets: Kluber, who’s in the running for the Cy Young Award, and Terry Francona, who just might win Manager of the Year.

"Terry has a way of breaking down barriers in our organization and getting people to talk to each other," said general manager Mike Chernoff. "He's always been able to connect, regardless of the situation or circumstance..

Francona hardly needs an introduction in New York, as his Red Sox became the only team to engineer a post-season comeback from 3-0 playoff deficit in 2004. Francona’s .618 winning percentage (66-41) is by far the best in the two-plus decades of the wild card playoff era.

And last year he almost became the only the fifth manager in the game’s history to win a World Series with multiple teams, joining Bucky Harris (1924 Senators, 1947 Yankees), Bill McKechnie (1925 Pirates, 1940 Reds), Sparky Anderson (1975-76 Reds, 1984 Tigers) and Tony La Russa (1989 A’s, 2006 and 2011 Cardinals).

Francona took the Indians all the way to Game 7 of the Fall Classic, and even then a champion wasn’t decided until the 10th inning. The Tribe fell short, but president of baseball operations Chris Antonetti nevertheless praised Francona for “a masterful job” turning the Indians into a powerhouse.

This season, he’s kept them at that level, despite missing two weeks - including his All-Star Game managerial gig - to undergo a cardiac ablation.

“He was always focused on, ‘How do we take what we have and figure out a way to make the team and individual players successful?’ “ Antonetti said. “He never worries about who’s not here and what adversity we face, but finding a way to overcome it. I think we’ve seen it over the course of the season and certainly throughout the postseason.”

What’s that mean for 2017? Truth is, the Indians could be even better this year, now that the industry is more clearly defined than ever between the Haves (Dodgers, Nationals, Astros, Red Sox, Yankees and Indians) and Have Nots (everyone else). The Indians will spend September doing calisthenics for the playoffs, with only six games against teams over. 500.

Not that they’ve struggled against the elite, either, posting a 26-13 record against the Astros, Yankees, Red Sox, Twins, Angels and Mariners – all of whom are either October-bound or have a realistic chance of getting there.

More than ever, what separates the good from the very good clubs, and what distills into a world champion after that, is the Game 1, 4 and 7 ace. Right now, that would have to be Kluber, who once again validated his larger-than-life status this week.

Kluber allowed the Yankees just three hits and two runs in a 6-2 victory, taking down Severino in the process. It was a psychological setback to the Yankees, who consider Severino their best hope in a wild-card playoff and in any Game 7 showdown against an opposing team’s ace.

No doubt Severino, 23, is a future star if he isn’t already. No one in baseball maintains his 98-mph fastball deeper into a game. But Kluber is a still a rung higher on the pyramid, leading the AL with a 2.63 ERA and 0.89 WHIP.

No wonder Kluber is nicknamed Klubot: he’s a machine when it comes to disassembling his opponents, even moreso this season. His 215 strikeouts to just 33 walks has produced a career-best 6.52 ratio.

“It's starting to get a little bit (boring), because you're getting no action out there,” centerfielder Bradley Zimmer told MLB.com this week. “It's like you're standing and watching him throw sliders and guys swinging over them. I've said this, I feel like, every time he pitches: The guy is unbelievable. I'm just happy he's on our side."

Perhaps even more remarkable is that Kluber is leading the charge for a pitching staff that’s missing Andrew Miller (knee), Danny Salazar (elbow), Josh Tomlin (hamstring). Throw in Jason Kipnis (hamstring) and Michael Brantley (ankle) and you have a roster sufficiently banged up that a 19-9 record in August should’ve been a longshot.

But the Indians are gaining momentum once again, even if it’s under the radar. Actually, this is how the Indians prefer it, deferring the headlines to the Yankees and Red Sox. But that doesn't make the Tribe any less dangerous. With October right around the corner, it'd be a mistake to underestimate them.